Next generation optical networks incorporate Physical Layer Impairment (PLI) aware routing and spectrum assignment (RSA) strategies to improve connection performance. PLI-aware RSA strategies require a large amount of physical layer data processing to detect and avoid impairments present in networks. Traditionally strategies have been based on maximizing network utilization (or minimizing a blocking probability). The main techniques employed include any one of: fixed routing (shortest path/fewest links), alternate routing, and adaptive routing.
Fixed routing requires the simplest calculations (shortest path length or fewest nodes) but leads to a higher blocking probability for a given network load. Alternate routing involves setting up at least a primary path and a secondary path. In the case of congestion on the primary path, the network can switch the traffic to the secondary path. Alternate routing requires real-time monitoring of network loads, and real-time determination of a “best” current network path. Adaptive routing is more efficient for data services as it includes consideration of congestion or failure of network links when making a network path decision.
Heuristic RSA schemes may combine both routing and wavelength assignment in a single optimization algorithm, but tend to be computationally intensive in comparison with fixed path routing and alternate routing methods. Accordingly, heuristic schemes are only rarely used (for instance at initial setup of permanent or for long-life connections).
A difficulty with the prior art solutions has been that there is a trade-off between optimum pathing and the computational load required to achieve that pathing. Theoretically optimal pathing may take a noticeably longer period of time to establish a connection between parties. From the communicating parties' perspective, the network speed is a function of both the time to establish the connection and the transfer speeds across the network once the connection has been established.
There is a need for an improved method of routing and wavelength/spectrum assignment for optical networks.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.